1. Field of Invention
This invention relates to an apparatus for removing condensate generated by fan coils that are employed in a heating, ventilation and air conditioning system such as a heat pump thermal distribution system or an air conditioner. More specifically, this invention relates to a novel apparatus that uses drain valves and a pump to remove condensate from fan coils. This invention is particularly applicable for condensate removal where gravity, long drain conduit runs, or other conditions impair condensate drainage. This invention permits a single condensate removal pump to service multiple fan coils.
2. Description of the Related Art
Heat pumps are used for air-conditioning in the comfort heating and cooling of space in commercial and residential structures. During the past decade, heat pumps have rapidly increased in popularity. The attractiveness of heat pumps is a result of their power efficiency as well as their increasingly competitive cost of purchase and installation. The present invention is used to remove condensate generated by heat pumps operating in the cooling mode.
Heat pumps are generally described in Heat Pump Manual, Electric Power Research Institute, 1985. A heat pump uses the same equipment to cool conditioned space in the summer and to heat it in the winter, maintaining a generally comfortable temperature within a structure at all times. Two heat exchange coils are used in a heat pump. One coil is located within the conditioned space while the other coil is located outside the structure. When heating the conditioned space, the inside coil serves as a condenser and the outside coil serves as an evaporator. When cooling the conditioned space, roles are reversed and the inside coil serves as an evaporator while the outside coil serves as a condenser. The heat exchange coil that is inside the structure and the heat pump equipment that is co-located with that coil are collectively referred to herein as the "inside unit." Their counterparts outside the structure are referred to herein as the "outside unit."
The present invention is used with heat pumps that distribute a cooling liquid to multiple areas. These multiple areas are typically separate rooms within a structure. Such areas are often referred to as "zones" and heat pumps that condition multiple zones are often referred to as having "multi-zone thermal distribution systems."
Multi-zone thermal distribution systems can be classified according to the type of fluid used for thermal distribution. The air-to-air system, the type of system that is presently the most common in use, employs air ducts to deliver cool air from the inside unit to vents located at each zone. The present invention is not used with air-to-air systems since their air vents do not produce condensate.
The air-to-water thermal distribution system, also known as the "hydronic" system, employs water conduits to supply cooling water from the inside unit to fan coils located in the conditioned zones. Such fan coils are referred to herein as "zone fan coils." In this system, the heat exchanger coil of the inside unit, which is refrigerant cooled, is used to cool supply water and is thus a refrigerant-water interface. Cooled supply water is pumped through a water supply conduit to the zone fan coils. Zone fan coils, cooled by the supply water, are a water-air interface. A fan blows air over the water cooled coil surface resulting in cooling of that air. After having cooled the zone fan coil, the water is pumped through a return conduit back to the inside unit for further use thus completing a supply-return water circuit.
Cooling a zone fan coil causes moisture in air to condense to form water condensation on cool coil surfaces. As condensate accumulates, it drips off the coil to collect in a drip pan for the zone fan coil. Removal of this condensate from hydronic zone fan coils is the focus of the present invention.
Another type of thermal distribution system uses zone fan coils but, in contrast to hydronic systems, employs a supply-return conduit to deliver cool refrigerant to zone fan coils. The refrigerant cools coil surfaces in the zone fan coils and the fan coils otherwise operate--and cause water condensation--similar to hydronic systems. Accordingly, the present invention may also be used to remove condensate from refrigerant driven zone fan coils.
Hydronic systems have advantages over both air-to-air systems and refrigerant driven zone fan coils. Cost of installation is usually lower for hydronic systems as compared to both air-to-air systems and refrigerant driven zone fan coils. Hydronic systems use compact water supply-return conduits in contrast to the relatively large, bulky and difficult to configure air ducts employed by air-to-air systems. These compact hydronic conduits are more readily routed through restricted wall cavities than bulky air ducts. Hydronic systems also offer an installation cost savings over refrigerant driven zone fan coils because a plumber can install a hydronic supply-return conduit while a more highly paid refrigeration technician is required to install supply-return conduit for refrigerant driven zone fan coils.
Conventional condensate removal systems provide the drip pan of each zone fan coil with a separate drain conduit that leads directly through a hole in an exterior structure wall or through a window. Condensate then drains directly to discharge points outside the structure at an above-ground level. This system relies upon gravity to produce condensate flow through removal conduits.
the through-the-wall, condensate removal system described in the previous paragraph, while appealing in its directness and simplicity, has limits. Absence of convenient holes through which to route drain conduits are one potential limitation. A fan coil servicing a zone that is not adjacent to an exterior structure wall or window would require a long run of drain conduit resulting in the routing problems and the flow problems of long runs. Drain conduit servicing fan coils located in a basement or in another type of below-ground zone cannot rely upon gravity to drain condensate to an above-ground discharge point. Moreover, even for above ground fan coils, conduit routing constraints may require upward conduit runs which would impair gravity driven condensate flow.
The conventional solution to the drainage problems described in the previous paragraph is to use condensate removal pumps located in each fan coil. Each fan coil with impaired drainage is fitted with a condensate removal pump to draw condensate to respective outside discharge points. This approach requires drainage conduits to the outside for each fan coil and requires separate condensate removal pumps for each fan coil. A requirement for multiple drainage conduit routes increases installation costs and a requirement for multiple condensate removal pumps increases system purchase cost. Each of the multiple pumps requires such related equipment as plumbing, electrical connections, wiring, and circuit breakers. Through-the-wall drainage to outside discharge points may also be undesirable for aesthetic or safety reasons such as exist in locations having pedestrian traffic. Accordingly, a novel condensate removal apparatus is desired which avoids these costs and limitations.